Measurement and investigation of PCC Point harmonics in a grid-tied PV station

This paper addresses the PCC-point harmonics in a parallel-inverter-based photovoltaic station. Firstly, the harmonic measurement of a grid-tied PV station has been implemented. The voltage and current waveforms present some significant characteristics, such as lower frequency, power correlation and inter-harmonic. The most of these harmonic currents flows through the inverter IGBT bridges and filter inductance branches, rather than the filter capacitor branches. These harmonics are 3-phase symmetric and contain 3^rd and 6^th harmonic components. These harmonics are not produced by the resonances related to the output LCL filters of PV inverters. This study proposes that the resonances between inverter and grid impedance are the dominant causes of the harmonics.